1. Field of the Invention
The present invention relates to a backlight module and a liquid crystal display (LCD) using the same.
2. General Background
LCDs are flat-panel displays which have excellent features including high resolution, physical thinness, light weight, and low power consumption. Their market size has expanded recently with improvements in display performance and production capacity as well as improvements in price competitiveness against other types of display devices.
A typical LCD is represented in FIG. 6. The LCD 300 includes a flexible printed circuit board (FPC) 310, a liquid crystal display panel 320, a frame 330, two light emitting diodes (LEDs) 340 cooperatively serving as a light source, and a light guide plate 400.
The FPC 310 includes a circuit region 311, and a light source accommodating region 312 for accommodating the two light sources 340. The circuit region 311 is electrically connected with the liquid crystal display panel 320. The accommodating region 312 is a strip portion extending from the circuit region 311. The frame 330 includes a depressed portion 331 having two cavities 332.
The LCD 300 is assembled according to the following steps. First, the light guide plate 400 is placed in the frame 330. Second, the accommodating region 312 with the two light sources 340 is placed in the depressed portion 331 of the frame 330, with the two LEDs 340 being received respectively in the two cavities 332. Third, the circuit region 311 of the FPC 310 is folded behind the frame 340 and the light guide plate 400. Finally, the liquid crystal display panel 320 is placed on the light guide plate 400, whereby the accommodating region 312 is sandwiched between the liquid crystal display panel 320 and the frame 330.
The liquid crystal display 300 has the following problems. First, due to limitations in manufacturing precision, the sizes of the cavities 332 are not exactly the same as those of the light sources 340. Consequently, gaps exist between the light sources 340 and the light guide plate 400, which affects the brightness of the light guide plate 400. Second, because the FPC 310 is bent, and the accommodating region 312 extends from the circuit region 311, the accommodating region 312 tends to be uneven. This results in a light emitting surface of each light source 340 facing an incident surface of the light guide plate 400 at an oblique angle. The oblique angles can diminish the uniformity of light output by the light guide plate 400.
FIG. 7 is a graph showing the negative impact of the above mentioned gaps on the effective utilization of light by the light guide plate 400. X represents the distance between the LEDs 340 and the incident surface (not labeled) of the light guide plate 400 in millimeters (mm), and Y represents the relative emitting luminance of the light guide plate 400. It is can be seen that the greater the value of X, the lower the value of Y. That is, the greater the gap, the lower the value of the relative emitting luminance.
Therefore, a new backlight module and liquid crystal display that can overcome the above-described problems are desired.